better balancing of the latency timer to decrease result byte fragmentation

git-svn-id: https://urjtag.svn.sourceforge.net/svnroot/urjtag/trunk@1074 b68d4a1b-bc3d-0410-92ed-d4ac073336b7

jtag/ChangeLog

@@ -1,9 +1,12 @@
 2008-02-21  Arnim Laeuger  <arniml@users.sourceforge.net>
 
+   * src/tap/parport/ftdi.c (ftdi_mpsse_open): set latency timer to 16ms
+   * src/tap/parport/ftd2xx.c (ftd2xx_mpsse_open): set latency timer to 16ms
+   * src/tap/cable/ft2232.c (send_and_receive): issue SEND_IMMEDIATE command
+       when receive bytes were scheduled
    * src/bsdl/bsdl_bison.y, src/bsdl/bsdl.h, src/bsdl/bsdl_flex.l, src/bsdl/bsdl.c:
        push mode and debug through init tree to avoid error message from scanner
        in simple test mode.
-
    * src/bus/fjmem.c: merged branches/jmem to trunk
        -> added fjmem bus driver
 

jtag/src/tap/cable/ft2232.c

@@ -73,6 +73,7 @@
 #define LOOPBACK_START 0x84
 #define LOOPBACK_END   0x85
 #define TCK_DIVISOR    0x86
+#define SEND_IMMEDIATE 0x87
 
 
 /* bit and bitmask definitions for GPIO commands */
@@ -257,6 +258,11 @@ send_and_receive( cable_t *cable )
 			bytes_sent++;
 		}
 
+		/* the SEND_IMMEDIATE command will trigger the ft2232 to send
+		   its bytes immediately without waiting for the latency timeout */
+		if (bytes_to_recv)
+			parport_set_data( p, SEND_IMMEDIATE );
+
 		/* Step 2: flush parport */
 		parport_set_control( p, 1 ); // flush
 		parport_set_control( p, 0 ); // noflush

jtag/src/tap/parport/ftd2xx.c

@@ -292,6 +292,14 @@ ftd2xx_mpsse_open( parport_t *parport )
 		FT_Close(fc);
 		return -1;
 	}
+        /* set a reasonnable latency timer value
+           if this value is too low then the chip will send intermediate result data
+           in short packets (suboptimal performance) */
+	if ((status = FT_SetLatencyTimer(fc, 16)) != FT_OK) {
+		fprintf(stderr, "Can't set target latency timer: %li\n", status);
+		FT_Close(fc);
+		return -1;
+	}
 	if ((status = FT_SetBitMode( fc, 0x00, 0x00 )) != FT_OK) {
 		fprintf(stderr, "Can't disable bitmode: %li\n", status);
 		FT_Close(fc);
@@ -312,11 +320,6 @@ ftd2xx_mpsse_open( parport_t *parport )
 		FT_Close(fc);
 		return -1;
 	}
-	if ((status = FT_SetLatencyTimer(fc, 1)) != FT_OK) {
-		fprintf(stderr, "Can't set latency timer: %li\n", status);
-		FT_Close(fc);
-		return -1;
-	}
 
 	return 0;
 }

jtag/src/tap/parport/ftdi.c

@@ -322,6 +322,17 @@ ftdi_mpsse_open( parport_t *parport )
 		ftdi_deinit(fc);
 		return -1;
 	}
+        /* set a reasonnable latency timer value
+           if this value is too low then the chip will send intermediate result data
+           in short packets (suboptimal performance) */
+	if(ftdi_set_latency_timer(fc, 16) < 0)
+	{
+		fprintf (stderr, "Can't set target latency: %s\n",
+			ftdi_get_error_string (fc));
+		ftdi_usb_close(fc);
+		ftdi_deinit(fc);
+		return -1;
+	}
 
 	if (ftdi_set_bitmode(fc, 0x0b, BITMODE_RESET) < 0)
 	{
@@ -330,7 +341,7 @@ ftdi_mpsse_open( parport_t *parport )
 		ftdi_usb_close(fc);
 		ftdi_deinit(fc);
 		return -1;
-	};
+	}
 	if (ftdi_set_bitmode(fc, 0x0b, BITMODE_MPSSE) < 0)
 	{
 		fprintf (stderr, "Can't set mpsse mode: %s\n",
@@ -338,7 +349,7 @@ ftdi_mpsse_open( parport_t *parport )
 		ftdi_usb_close(fc);
 		ftdi_deinit(fc);
 		return -1;
-	};
+	}
 
 	if (ftdi_usb_reset(fc) < 0)
 	{
@@ -357,14 +368,6 @@ ftdi_mpsse_open( parport_t *parport )
 		return -1;
 	}
 
-	if(ftdi_set_latency_timer(fc, 1) < 0)
-	{
-		fprintf (stderr, "Can't set minimum latency: %s\n",
-			ftdi_get_error_string (fc));
-		ftdi_usb_close(fc);
-		ftdi_deinit(fc);
-		return -1;
-	};
 
 	return 0;
 }